Water heater



FIG. 1 is a perspective view of a water heater showing our new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is a top plan view.

The portions of the water heater shown in dashed lines in FIG. 4 do not form a part of the claimed design. 

The ornamental design for a water heater, as shown and described. 